Control system for electric motors.



A. O. EASTWOOD & H. F STRATTON.

CONTROL SYSTEM FOR ELEGTRIGMOTOBS.

I A PPLIOATIOH I'I LED MAB. 18, IBIQ. 1,008,453.

Patented Nov. 14 1911 our control system with the master switch mats oil-position; F1 motor circuits when t e conventionally clearly understood in the description of the b, the brush .D,

' slcwl the hoisting 'd UNITED STATES PATENT OFFICE.

ARTHUR C. EASTWOOD 01110, A coRroR 'rIon or 01110.

, AND HARRY E. STBATTON, TO THE ELECTRIC CONTROLLER Ann MANUFACTURING COMPANY,

or cLEvELAnn, 01x10, AssrGNoRs or CLEVELAND,"

coErRoL' sYs'rEu FOB ELECTRIC EroToRs.

To all whom it may concern: I

ARTHUR 0. EAST- Be it known that we, W001) and HARRY F. STRAr'roN, citizens of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented or discovered new and useful Improvements in Control Systems for Electric Motors, of which the following is a specification. i v

Our invention relates to systems and methods for controlling electric motors and has particular reference to hoistin systems, though it ma be used in other re ation s. A

It is the ob ect of our invention to provide mean""-"f-or obtaining slow speeds in lowering loads driven by a motor having a series field winding ,-but co'nnccted while lowering with its said field separately excited.

' Referring to the accompanying drawings, Figure 1 is a diagram showing one form of 2,.a diagram of the master'switch is in its first hoisting position; Fig. 3, a' diagram of the motor circuits when the masterswitch is in its first lowering position; and Fig. 4, a diagram similar to Fig. S'showing the motor circuits when the master-switch is in its last or full-on position;

On the drawings, A represents the armature, F its series field, B the winding of the magnetic brake B, and G the master-switch or controller having a pair of brushes and a number of controller contacts for control-.

ling the, resistances R and R in an evident manner. The connection of. the var ous shown ..elements ,wlll be operation following.

With the master-switch arni D on the first hoisting .positiop shown by the line hit, the

motorcircuit is as follows: from the positive through the wire 1, the contact 0', the brush D, the contacts a and 1", the resistance R, he wire 7, the armature A, the wire 6, the resistance R the contacts b and the contact 0",. the wires 5 and 4, the winding B of the'brake B ,the field Rand the wire .2 to the negative. The current in this circuit starts the motor irectiom As the arm is movedfarther toward the fulljon position, the'fresi'stances are gradually cut out in an obvious manner until finally the flpeciflcationof Letters Patent. Application filed March 18, 1910. Serial No. 550,208.

motor is connected directly across theline.

' gravity stops the load, and

[and the wires 8, 3, and i contact 1, the brush Patented Nov. 14, 1911.

As the arm D is thus moved the motor peed is gradually increased. In all the positions of the arm D the brake Wilding B receives which holds the the full motor current, brake B released in a" wellknown manner. When it is desired ,to stop the movement of the load-the arm D is moved to the off position. The resistances R and R are gradually inserted in motor circuit, which is finally opened at the oflf position, cutting off the source, of current supplr. The action of since no current now flows 1n the brake winding, it sets and prevents the load descend .ng'. When-it is desired to lower the load t 1e controller arm 1s moved to the first position lowering shown by the line, 7010.

The operating solenoid "i of switch H is j energized by a current whose circuit is'as follows: from the ositive through the wire 1, the contact 0 e brus'i D, the contact c, the wire 9, the magnejzing winding-h to the negative.

This current causes the sw .tch H to close its so, postive through the contacts h, k. The mototr circuits are now as follows: from the wire 1, the contact 0 theorush D and the Contact 6', and the point 0', where thecurrentdivides, one branch passing through the resistance R ,the wire 4, the brake winding B, the field F, and the wire 2 to the negative; the other branch which begins at thepoint O passing'through theresistance It andthe 'wirefi to the point 0, where it divides, one part passing through the armature A in the opposite direction to tha; in hoisting, the wire 7, the resistance R, the contact 1, the brush -D, the contact 0*, and thewires 3 and 2 to the negative; and the other part starting at the point 0, at d passing through the resistance It, the'wii'e 11, the contacts 72. and h" of the switch It, the wire 10, the

D zhe contact 0, and

.the wires 3 and 2to the negative. The simplified motor circuits just traced are shown 109 in Fig. 3.

It will be mutt-1 that there-are. now two parallel circuits establishld through the me tor, one of these 'contairin the, t'esistance the brake winding B, anil F; the otheniincluding th e resistance R a parallel circuit containi [1E series with the resistance as one branch,

theseries field 1 05 the armature in i and the resistance ,R and the switch H as the other. The resistance R is so propor-' ,tioned'that it will allow approximately full load current to flow through the series field 'F, and the motor field is, therefore, fully energized. The armature A and the resistance R in the armature circuit are shunted by the'resistance B through the switch H. Therefore, the total current passing in'the armature branch through the resistance R is not allowed to pass through the armature of the motor, and it, therefore, will operate at a very slow speed, depending on the value of the resistance R. Also, when a heavy loaddrives the motor, as .a dynamo, this shunt produces slow speed. By this means a low speed is obtained either with a light load or a heavy load in lowering.

In order to increase the speed, the arm D- of the controller C is,moved toward the full on osition, gradually cutting the re.

sistanee out of the armature circuit and inserting it in the shunt; and at the same time cutting the resistance R out of the armature branch of the parallel circuit and inserting it in the field branch. This increases the speed of the motor from three causesffirst, by decreasing the amount of a resistance in series with the armature '30 branch; second, by weakening the field by inserting resistance in the field branch; and third, by increasin the resistance in the "armature shunt. W en the controller arm D reaches the last point, all of the resistance R ;is' cut out of the armature circuit and inserted in the shunt, and there are then three parallel paths across the supply mains;

one throu h the resistance R and R, and

brake an series field windings; a second through the, armature A; an,

unless the contact a is shortened as now to' be described, a third through the resistance R", theswitch H, and the resistance R. It is not necessary that the current through the through this path of the circuit.

resistance R be used on the final controller point since the armature, is connected directly across the line; and by making the contact a so short as to make the brush D 1 leave theco'ntact 0 on the controller just before the last point b of the controller C is reached, the switch H will be caused to open, thus preventing the loss of current The simlified motor connections for the final lowerlug-position are shown in Fig. 4:. \Vhen it is desired to slow down or stop the load,v

the arm D of the controller C is moved to ward the off position, shown on Fig. 1. As soon as the brush D makes 'contact with the contact a the switch H again" closes, and

the slowing down of.the speed is accomplished under the shunted armature condition as. describedabove, the current through the series field varying as the resistance. R is cut out of its circuit. As the 'arm apa circuit 0 proaches the contacts 1' and b the speed of the motor becomes very slow, and when the controller handle is brought to the oil position the current through. the motor is inter rupted, and the series brake B sets, bringing the motor to rest and holding the load.

We do not limit our invention to series Wound motors or brakes, nor to any definite type of-controller, nor to other details and combinations thereof unless required by the prior art or by language in'the claims which permits of no other construction.

We claim- 1. In an electric control system, a motor having armature and field windings, means connecting the armature and field windings in parallel paths, a resistance means for placing it in each path, and a circuit of low resistance, shunted around Y the armature winding.

having armaturealnd field windings, means connecting the armatureand field windings in parallel paths, a resistance means for placing it in each path, a circuit of low resistance, shunted around the armature winding, and means for subsequently opening said shunt circuit. I

3. In'an electric control system, a motor having armature and field windings, means connecting the armature and field windings in parallel fpaths, a resistance in each path,

controller is moved toward the full on position. 1

4. In an electric control system, a motor "having an armature winding, means connecting the armature winding across thesupply mains,

a variable resistance in series with the armature winding, a circuit of low I .85 2'. In an electric control system, a motor low resistance arranged to include the armature windingand its resistresistance paralleling the armature winding and said variable.resistance, and means by which the variable resistancemay be simultaneousl cut out of the armature circuit and cut intothe parallel circuit.

5. In an electric control system, a motor having an armature winding, means connecting the armature winding across the supply mains, 'a variable resistance in series with the armature winding, a circuit of low resistance paralleling the armature winding and said variable resistance, means by which the variable resistance may be simultaneously cut out of the armature circuit and cut and increasing the speed thereo the motor increasing intoj"the parallel circuit, and means for openshunt circuit the resistance i the resistance iii the armature path, and increasing the resistance in the shunt circuit. In "an electric control system, a. motor having an armature winding, means connecting the armature winding acrossthe supply mains, a circuit of low resistance in parallel with the armature Winding, a resistance in the armature branch of the parallel circuits, and means for decreasing the said resistance and for inserting resist-an: in the parallel circuit. t

8. In an electric control system, a motor having armature and field windings, means connecting the armatureand field windings the field path, decreasing I in series for operating the motor in one direction, and for operating it in the other direction means connecting the armature and field windings in paralle. paths,a resistance in each path, a circt it of low resistance shunted around the a1 mature winding, and means for opening 1he shunt circuit.

Signed at Cleveland, Ohio, this 16th day of March, 1910.

ARTHUR C. EASTWOOD. H. F. STRATTOINT. Witnesses:

J. H. HALL, H. M. DIEMER.

Coplel of this patent may be obtained for live cents each, by eddressing the Commissimer of Patents.

Washington, D. 0. 

